HSC Survey Results

Scots Bay Survey # 10 Results from 24/09/2023

Survey Details

4 commercial purse seiners conducted this fishing survey on 24/09/2023 starting at 20:00:00, which was 0.57 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 3,420mt, and with turnover applied 2,997mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
C1 T01 2023-09-24 23:49:49 2023-09-25 02:36:41 -65.224 45.096 -64.746 45.254 SB 42.76 8.30
C1 T02 2023-09-25 03:03:44 2023-09-25 05:19:36 -64.826 45.311 -65.234 45.167 SB 36.99 8.82
FM T01 2023-09-25 00:44:21 2023-09-25 04:05:23 -65.232 45.037 -64.681 45.217 SB 47.97 7.73
FM T02 2023-09-25 04:34:56 2023-09-25 06:57:49 -64.769 45.270 -65.213 45.117 SB 38.98 8.84
LM T01 2023-09-24 23:31:26 2023-09-25 02:34:36 -65.235 45.054 -64.705 45.230 SB 46.41 8.21
LM T02 2023-09-25 02:59:12 2023-09-25 05:20:25 -64.783 45.285 -65.231 45.129 SB 39.43 9.05
MS T01 2023-09-24 23:45:12 2023-09-25 02:48:54 -65.225 45.076 -64.728 45.242 SB 45.26 7.98
MS T02 2023-09-25 03:18:21 2023-09-25 05:38:13 -64.806 45.297 -65.222 45.152 SB 37.49 8.68

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
C1 T01 -35.5 -52.169 0.022
FM T02 -35.5 -57.701 0.006
LM T02 -35.5 -60.346 0.003
MS T02 -35.5 -60.606 0.003
LM T01 -35.5 -61.412 0.003
C1 T02 -35.5 -61.754 0.002
FM T01 -35.5 -62.206 0.002
MS T01 -35.5 -68.025 0.001
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 661 -58.3618 0.0052 3,419.932 77.5 NA 1,583.85 46.31
Northern Box NA 77 NA NA NA 9.0 NA NA NA
Eastern Box NA 115 NA NA NA 13.5 NA NA NA

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by C1, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by C1, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2023-05-22 40,856.000 40,856 2022-05-29 92,542 92,542 99,092 99,092
Scots Bay 2 2023-06-06 113,767.329 108,783 2022-06-12 93,163 80,663 113,792 100,407
Scots Bay 3 2023-06-18 34,279.387 15,158 2022-06-26 30,535 17,624 29,429 13,709
Scots Bay 4 2023-07-02 11,744.776 5,113 2022-07-10 9,886 5,432 7,892 3,515
Scots Bay 5 2023-07-16 19,282.634 17,575 2022-07-26 11,954 10,869 11,402 10,536
Scots Bay 6 2023-07-30 4,549.933 1,904 2022-08-07 4,900 2,901 6,150 4,248
Scots Bay 7 2023-08-13 4,298.806 3,616 2022-08-21 4,094 3,225 4,688 3,656
Scots Bay 9 2023-09-10 3,053.669 2,916 2022-09-18 7,275 4,212 7,283 0
Scots Bay 10 2023-09-24 3,419.932 2,997 2022-10-03 4,573 3,613 4,152 0
Scots Bay 8 2023-08-27 2,896.659 2,300 2022-09-05 20,439 19,939 21,420 20,848
Scots Bay 11 2023-10-09 3,387.515 2,971 NA NA NA NA NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2022 Scots Bay 279,361.0 241,020 305,300 256,011
2023 Scots Bay 241,536.6 204,189 NA NA

Tagging, Plankton, and CTD Data

Tag Data

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number SB2023-17 SB2023-18
Ground SB SB
Date 24/09/2023 24/09/2023
Wind Direction (km/h) NE NE
Swell (m) 0 0
Air Temp (c) 13 13
Tow Details
Tow Start 18:41:00 19:00:00
Tow End 18:51:00 19:10:00
Start Lat 45.05583 45.05133
End Lat 45.05617 45.05167
Start Lon -65.21300 -65.20167
End Lon -65.18550 -65.21533
Avg Tow Depth (m) 1.402012 1.476101
Speed 7.1 3.8
Heading 87 270
Tide Direction with against
Other Data Collection
Flow Start 320581 377915
Flow End 377915 438683
No. Revolutions 57334 60768
Distance (m) 1540.737 1633.018
Volume 4840.224 5130.128
Secchi Disappear (m) 9 9
Secchi Reappear (m) 8 8

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2023-17, which was with the tide and had an average depth of 1.4020125m. The second tow is SB2023-18, which was against the tide and had an average depth of 1.4761008m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2023 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.45. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.